Jerks in the SMG box in BMW – what is the cause and how to fix it?

Driver’s question – SMG transmission in BMW

I have a problem with the first generation SMG five-speed transmission. The problem is the “waving” of revs when changing gears. In addition, when shifting from two to three you can hear a deafening knock coming from the transmission most mechanics say it is the suspension. I have already replaced everything and the problem remains.

The second problem is the INPA software adaptation. It ends with a red message – “gearbox is not adapted”. However, I managed to adapt the clutch. I have a new dual mass clutch and the clutch does not leak when changing gears. You can clearly see as if the clutch would take on two times, as if the clutch is clipping. Please support.

The problem affected BMW 3 E46, but it also happens in other models with SMG transmission.

BM Cars service response – how should the SMG transmission work?

The described problem of the SMG transmission is often encountered in models with significant mileage (more than 200,000 km). With a well-functioning clutch and the right amount of oil in both the clutch system and the transmission, gear shifting is quick with a gently perceptible jerk.

Typically, with high mileage and unchanged oil in the transmission, significant resistance begins to appear, which prolongs the gear shifting phase. This can manifest itself in the form of a perceptible jerking of the vehicle. If, on top of this, there are leaks from the clutch system, then there are problems with gear shifting and the failure mode of the transmission operation appears.

A functioning transmission must not make any noises during gear shifting. Also, the adaptation of the clutch must be completed successfully. The described message about the unfinished adaptation process indicates a problem with the clutch itself or mechanical wear of the transmission.

The repair of SMG transmissions itself is also a problem. There are currently no parts available for SMG transmissions. There are also few places remanufacturing clutches. In this situation, the fastest repair option is to replace the box with another used one in better condition.

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